Automotive tubes and hoses, as well as hoses employed in similar environments, which provide for the transmission of various fluids and gases, have historically been fabricated by vulcanizing rubber with thermosetting compositions. These hoses have proven to be advantageously flexible and resistant to various fluids with which they contact. Also, fibers, such as continuous fiber cord, have been incorporated into the hose to provide useful burst strength, which is particularly advantageous in environments that experience variation in pressure.
While thermoset hoses have proven to be technologically useful, their method of manufacturing can be inefficient and limited by known techniques for forming thermoset rubber articles. Also, because the rubber is cured, the ability to recycle the hoses or materials from which they are made is severely limited.
Thermoplastic vulcanizates include blends of dynamically cured rubber and thermoplastic polymers. The rubber may be dispersed within the thermoplastic resin phase as finely-divided rubber particles. These compositions have advantageously demonstrated many of the properties of thermoset elastomers, yet they are processable as thermoplastics.
Thermoplastic vulcanizates have been advantageously employed to make hoses. These hoses can be efficiently fabricated by using extrusion techniques that take advantage of the melt processability of the thermoplastic vulcanizate. Also, the ability to melt process the thermoplastic vulcanizate allows for flexibility in recycling the hoses and the thermoplastic vulcanizate compositions.
The prior art has further recognized that advantages can be realized by reinforcing thermoplastic compositions with chopped fibers. Indeed, Campbell and Goettler explain methods for extruding articles, such as hoses, made from polyvinylchloride compositions where advantageous fiber alignment has been achieved. See THE REINFORCEMENT OF THERMOPLASTIC ELASTOMERS WITH SANTOWEB FIBRE®; The Plastics and Rubber Institute, International Conference at Brunel University, Uxbridge, Middlesex, UK, (1985).
Similar technology has been applied to thermoplastic vulcanizates as taught in U.S. Publication No. 2006/0186583. While the use of aligned, chopped fibers has proven advantageous, the prior art recognizes a need for adhesion between the fiber and the plastic matrix. Poor adhesion between the fiber and the plastic matrix is believed to deleteriously impact the extensibility of the thermoplastic vulcanizate. In view of this, U.S. Publication No. 2006/0186583 teaches the use of treated fibers.
Also, WO 2005/021643 A1 teaches thermoplastic elastomer compositions that include (i) a thermoplastic rubber blend, (ii) a functionalized polyolefin, (iii) a crosslinking agent selected from resins obtainable by reacting melamine, urea, benzoguanamine and/or glycoluril with formaldehyde, epoxy and isocyanate resins, and (iv) adhesion activated fibers.
Despite these advancements, improved compositions with better adhesion between the fiber and plastic matrix remains a goal because of expanding uses and needs, particularly in the automotive industry.